Murine coronavirus mouse hepatitis virus (MHV) causes encephalomyelitis and demyelination in rodents. It has been used as a model system for studying human multiple sclerosis. The long-term goals of the propose investigation are to elucidate the molecular mechanism of neuropathogenesis of MHV. The specific objectives are focused on development of novel defective-interfering (DI) RNA of MHV as a vector system to express viral genes encoding the spike and the hemagglutinin/esterase proteins, concomitant with viral infection, and determining the role of these proteins in viral neuropathogenesis. The system will also be used to assess the molecular mechanism by which these viral proteins are incorporated into virus particles. In addition, cytokines and cytokine antagonists will be expressed via the DI RNA vector and their effects on viral replication in vitro and in vivo will be assessed. Distributions of the expressed proteins and histopathological changes of the central nervous system will be evaluated by immunoenzyme-staining of the sections of mouse brains and spinal cords using antibodies specific for the proteins and histological examinations. This vector system will provide a unique way of expressing viral proteins without the use of a foreign vector and assure the synthesis of viral proteins by the same mechanism as the authentic viral proteins. Furthermore, the foreign genes such s cytokines, can be locally expressed in the central nervous system, thus, providing a direct way of assessing the effects of cytokines or cytokine antagonists on viral infection. The results gained from this study will provide fundamental insights into the mechanism of neurological diseases and viral pathogenesis in general.